MoOx/SBA-15丙烷选择氧化催化剂的研究

采用浸渍法制备了一系列不同Mo含量的MoOx/SBA-15催化剂,并考察了丙烷选择氧化生成醛类含氧化合物（甲醛、乙醛和丙烯醛）的催化剂性能,利用FT-IR和XRD等技术对催化剂及载体的物化性能进行了表征。结果表明,催化剂的活性主要取决于Mo的负载量,当x(Mo)=1.75%［n(Mo)∶n(Si)=1.75∶100］时,醛类选择性约30%,总醛收率为10.4%,高分散催化剂尤其有利于醛类含氧化合物的定向生成。     

SbOx‐promoted pt nanoparticles supported on CNTs as catalysts for base‐free oxidation of glycerol to dihydroxyacetone

Understanding of selective base‐free oxidation of glycerol to dihydroxyacetone (DHA) over Pt‐based catalysts is of paramount scientific and industrial importance. In this work, a comparative study between differently sized SbO_x‐promoted and unpromoted Pt/CNTs catalysts is carried out to decouple the promoter effects from the metal size effects. The introduction of SbO_x appears to enhance both the glycerol oxidation activity and the DHA selectivity, and the largely sized promoted Pt/CNTs catalysts afford a relatively high DHA yield and less C–C bond cleavage. X‐ray photoelectron spectroscopy measurements reveal that the Sb species are mainly in the form of SbO_x, and the differently sized promoted catalysts show similar metal binding energies. Furthermore, theoretical studies on the promotional effects of SbO_x are carried out by DFT calculations. It is found that the presence of the promoter on the catalyst surface favors the preferential activation of the secondary hydroxyl group. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3979–3987, 2018     

Ultra-long Pt nanolawns supported on TiO2-coated carbon fibers as 3D hybrid catalyst for methanol oxidation

In this study, TiO₂ thin film photocatalyst on carbon fibers was used to synthesize ultra-long single crystalline Pt nanowires via a simple photoreduction route (thermally activated photoreduction). It also acted as a co-catalytic material with Pt. Taking advantage of the high-aspect ratio of the Pt nanostructure as well as the excellent catalytic activity of TiO₂, this hybrid structure has the great potential as the active anode in direct methanol fuel cells. The electrochemical results indicate that TiO₂ is capable of transforming CO-like poisoning species on the Pt surface during methanol oxidation and contributes to a high CO tolerance of this Pt nanowire/TiO₂ hybrid structure.     

环己烷在Au-Co/SBA-15上选择性氧化的研究

以沉积-沉淀法制备了Au-Co/SBA-15催化剂,在没有任何有机溶剂或助剂的条件下,研究了以空气为氧化剂的环己烷选择性氧化。当Au-Co/SBA-15催化剂中金的质量百分含量为1.0%,催化反应在423 K 3.0 MPa下进行120 m in时,催化效果最好,此时环己烷的转化率为22.7%,环己酮和环己醇的总选择性为95.2%,酮醇比为2.9,且催化剂重复使用五次后活性基本不变。     

Bimetallic gold/palladium catalysts for the selective liquid phase oxidation of glycerol

A new methodology for the preparation of single phase bimetallic Au–Pd on activated carbon (AC) has been recently developed and now used for preparing Au/Pd catalysts at different atomic ratio. The bimetallic catalysts have been tested in the liquid phase oxidation on glycerol in water using oxygen as the oxidant and compared with monometallic Au and Pd catalysts. We observed that strong synergistic effect is present in a large range of Au/Pd ratio, being maximized for Au₉₀–Pd₁₀ composition. Gold-rich composition showed an increased durability compared to palladium-rich alloy.     

Pt/C催化剂制备方法的选择

研究了以HCl酸洗、H_2O_2、浓H_2SO_4、HNO_3氧化处理后的活性炭为载体,用不同方法制备了Pt担载量为3%的担载型Pt/C催化剂。TEM统计结果表明,HCl酸洗、HNO_3氧化活性炭为载体,甲醛还原法制备的催化剂分散度最高,平均粒径最小为2．2nm。FT-IR结果表明,HNO_3氧化处理活性炭,活性炭表面含氧基团明显增加。     

负载型Pd/SBA—15催化剂催化性能研究

将负载型催化剂Pd/SBA—15用于催化邻氯硝基苯加氢。考察了反应温度、催化剂用量对Pd/SBA—15催化性能的影响,并考察了催化剂的使用寿命。实验结果表明,Pd/SBA—15催化剂表现出很好的催化性能,有望应用于工业生产。     

New approaches to designing selective oxidation catalysts: Au/C a versatile catalyst

Selective oxidation is of key importance in the synthesis of chemical intermediates. For many years a number of oxides and supported metal catalysts have been used. The key questions involved in the design of selective oxidation catalysts are discussed in the initial part of this paper. One of the most exciting recent developments in the field of selective oxidation has been the discovery that supported gold catalysts are active. The second part of the paper discusses Au/C catalysts, which are shown to be particularly versatile for oxidation reactions. Four examples of selective oxidation are described using molecular oxygen as oxidant: (a) selective oxidation of glycerol to glycerate in the presence of base; (b) the oxidation of cyclohexane to cyclohexanol and cyclohexanane in the presence of a radical initiator; (c) the oxidation of hydrogen to hydrogen peroxide, and (d) the oxidation of benzyl alcohol to benzaldehyde under solvent free conditions. In contrast, the Au/C catalysts are not active for oxidation of carbon monoxide at ambient temperature. These examples demonstrate that there exists a rich potential for Au/C as a selective oxidation catalyst and that research efforts should now be focussed on selective oxidation using supported gold catalysts.     

Preparation and characterization of Pt/HMFI–SBA-15 hybrid catalyst for tetralin transformation

A Pt catalyst supported on a hybrid material, HMFI–SBA-15, was prepared. Both, support and catalyst (Pt/HMFI–SBA-15) were characterized by nitrogen physisorption, small and wide (2θ) angle XRD patterns, FT-IR, SEM and HRTEM. The acidic properties of the hybrid material were studied by cumene dealkylation and those of the catalyst were studied by FT-IR of adsorbed pyridine. The catalyst, Pt/HMFI–SBA-15, was tested for tetralin transformation at various reaction temperatures 498, 523, 548, 573, 585 and 598 K. Wide-angle XRD and FT-IR in the skeletal region indicate the presence of MFI zeolite fragments incorporated onto SBA-15. The characterization of the acid sites on the support by cumene dealkylation and FT-IR pyridine adsorption revealed the presence of Brönsted acid sites related to the HMFI zeolite fragments in the hybrid materials. For the catalyst, a homogeneous distribution of Pt clusters was found by HRTEM. In the transformation of tetralin, at all the reaction temperatures, the main products were trans + cis-decalins. However, at high reaction temperature ring contraction to spirodecane and dehydrogenation to naphthalene were observed. At 598 K, a maximum of 8% of ring contraction products was obtained.     

Dendritic SBA-15 supported Wilkinson's catalyst for hydroformylation of styrene

After PAMAM (polyamidoamine) dendrimers have been successfully grown in SBA-15 mesoporous materials, Wilkinson's catalyst (RhCl(PPh₃)₃) precursor has been tethered on these dendritic supports to produce heterogeneous catalysts for hydroformylation reaction of styrene. SBA-15 has been functionalized by two methods. In the passivation method, the silanols outside the SBA-15 pores have been passivated to preclude the rhodium precursor to be tethered outside the channels. The rhodium catalysts supported in the pore channels of this passivated SBA-15 show positive dendritic effects in enhancing the catalytic activity, regio-selectivity and stability of the catalyst by minimizing the leaching of the rhodium complex catalyst from the catalyst support to the liquid-phase media.     

碳纳米管负载CuO-CeO_2催化剂用于CO选择性氧化

分别以碳纳米管(CNTs)和68%浓HNO3处理的CNTs为载体,采用超声辅助的浸渍法制备负载型Cu O-CeO_2复合氧化物催化剂,用于富氢气中CO选择氧化。采用XPS和LRS对预处理前后CNTs管的结构与表面性质进行研究。采用XRD和H2-TPR对催化剂结构进行表征。结果表明,经浓HNO3处理的CNTs载体表面含氧官能团—COOH相对含量提高了约68%,且表面缺陷增多,有助于催化剂活性组分的沉积和分散。以此负载的Cu O-CeO_2催化剂上Cu O物种具有较好的分散性,晶粒尺寸较小,催化剂表现出强的低温氧化还原能力,且表面CO氧化活性位增多,对CO选择性氧化具有低温高活性,T50低至90℃,反应温度低于140℃保持高选择性,且CO完全转化反应温度窗口拓宽宽至30℃。     

添加Sm对Pt /SBA-15催化苯完全氧化反应活性和热稳定性的影响

以Pt/SBA-15为催化剂,考察催化剂载体中添加Sm对于苯的完全氧化反应活性和热稳定性影响。采用了一种简便的记录起燃温度曲线和催化剂热稳定性评价方法,即向装载好催化剂的固定床反应器中持续通入恒定流量的反应气,逐步阶段性升高反应温度,同时在线检测出口尾气的浓度变化, 得到起燃温度曲线后,继续提高反应温度,然后恒定在某一设定的温度(如550℃)持续运行较长时间, 期间定时在线取样分析,如果有必要还可以连续考察降温情况下催化剂的反应活性情况。研究结果表明,几种催化剂低温活性次序为：Pt/SBA-15≈Pt/4%Sm₂O₃/SBA-15> Pt/Sm₂O₃> 4%Sm₂O₃/SBA-15,而对于高温稳定性则是Pt/4%Sm₂O₃/SBA-15> Pt/1.2%Sm₂O₃/SBA-15> Pt/SBA-15,Pt/Sm-SBA-15(SG)> Pt/SBA-15(SG)。总之,Sm的添加虽然未能提高Pt/SBA-15的低温催化活性,但是能明显提高催化剂在高温情况下活性的稳定性。1%Pt/4%Sm₂O₃/SBA-15同时具备较好的低温催化活性和高温稳定性,具有较好的应用前景。     

The catalytic reactivity of titanium dioxide supported on SBA-15 catalyst for selective oxidation of benzyl alcohol

Journal of Porous Materials - Titania doped Mesoporous SBA-15 with various metal ratios was prepared by wet chemical route. Several phyisco chemical methods were applied to determine the structural...     

甘油催化氧化合成二羟基丙酮研究进展

对甘油选择性催化氧化转化为二羟基丙酮的研究进行综述,介绍了负载型催化剂在不同条件下对产物选择性和反应物转化率的影响,以及催化剂的作用机理。阐述了甘油催化氧化存在的问题以及发展前景。从均相到非均相催化,从单金属到双金属负载催化,从金属到非金属催化,甘油氧化反应的研究不断在完善。研究发现用Bi改性的Pt负载催化剂可以有效地将甘油选择性催化氧化为二羟基丙酮,在最优条件下,可获得较高的甘油转化率和二羟基丙酮选择性,但催化剂稳定性较差,有待进一步提高。杂多酸催化剂以及非金属催化剂也存在稳定性差的问题。指出改善催化剂的稳定性将是未来研究的主要方向。     

Zn(Al)O复合氧化物负载Au催化剂催化氧化甘油制备1,3-二羟基丙酮

以尿素为沉淀剂,采用均匀沉积沉淀法制备了Zn(Al)O复合氧化物负载Au催化剂,并用于无碱条件下催化氧化甘油制备1,3-二羟基丙酮（DHA）反应,值得注意的是随着载体中Zn/Al摩尔比的不同,负载Au催化剂的催化活性和产物DHA的选择性呈现明显差距。结合X射线衍射（XRD）、X射线光电子能谱（XPS）、透射电镜（TEM）、CO吸附傅里叶变换红外光谱（CO吸附FTIR）等表征手段,发现载体Zn(Al)O复合氧化物中Zn/Al摩尔比会影响表面氧物种的含量并进一步会影响催化剂的催化活性和选择性。当Zn/Al摩尔比为7∶1、反应温度为80℃、氧气压力为10bar、反应2h时获得最佳的甘油转化率（58.5%）和DHA的选择性（95.3%）。同时,还考察了反应温度、反应时间、反应压力及载体的焙烧温度对催化性能的影响,并发现反应条件对催化剂的催化活性和选择性均有不同程度的影响。此外,以Au/Zn(Al)O-7∶1催化剂为基准考察了催化剂的稳定性,并通过表征手段分析了催化剂失活的主要原因。     

甲醇选择氧化一步法制甲缩醛催化体系研究进展

介绍了甲醇选择氧化一步法制甲缩醛的反应机理,研究了甲醇选择氧化一步法制甲缩醛催化体系的进展情况,详述了贵金属、杂多酸、钒基及其他催化体系.指出甲醇在催化剂作用下选择氧化一步法制甲缩醛工艺流程短,有利于降低生产成本,极具应用前景.最后对甲醇催化氧化一步法制甲缩醛提出了一些建议.     

Na改性Pt/AlOOH对甲醛催化氧化反应活性的影响

具有晶面取向的阳极氧化AlOOH因其低温甲醛催化性能而被用于催化氧化甲醛体系。为丰富AlOOH表面羟基含量,采用Na₂CO₃为Na前体浸渍法改性载体,制备不同Na含量（0.13%、0.19%、0.30%、0.41%,质量分数）的Pt/Na_x/AlOOH催化剂。通过BET、FTIR、XPS、HRTEM等表征分析,发现加入Na后,Na/AlOOH的表面羟基更加丰富,Pt/Na_x/AlOOH催化剂的比表面积增大,拥有更小的Pt颗粒尺寸,表面Pt颗粒分散度提高,Pt0元素价态含量增加。当Na含量为0.41%时,催化剂Pt/0.41Na/AlOOH的Pt分散度高达56%。实验结果证明,Pt/0.41Na/AlOOH展现出最优的HCHO催化活性,60℃时HCHO转化率达100%。